Needle shield for a prefillable syringe

ABSTRACT

A syringe assembly includes a needle sheath that has a cavity that receives a needle cannula. The needle sheath can be formed of materials such as thermoplastic elastomers or plastics yet still be utilized with conventional gas sterilizing processes. The needle sheath includes a passage that permits the sterilizing gases to enter the cavity while preventing entry of microorganisms into the cavity. Thus, a syringe assembly is provided that facilitates sterilizing a needle after the needle sheath has been placed over the needle.

BACKGROUND OF THE INVENTION

[0001] This invention generally relates to a syringe assembly having aneedle sheath.

[0002] Increasingly, medicaments are supplied from manufacturers inprefilled syringe assemblies. Such assemblies include a syringe that hasa needle cannula and is filled with the medicament. Typically, a needlesheath covers the needle cannula to prevent accidental contact with theneedle. Manufacturers supply such syringe assemblies as prepackaged,sterile, single use units. Thus, it is necessary to create a syringeassembly than can be sterilized after the needle sheath is placed overthe needle cannula.

[0003] In the past, needle sheaths were primarily composed of rubber.With the advent of modern thermoplastic elastomers, many manufacturershave switched to thermoplastic elastomers as the material of choice forneedle sheaths. Thermoplastic elastomers offer the advantages of being:cleaner than natural rubber products; providing better dimensionalcontrol of parts; available in a wider variety of synthetic materials toinsure compatibility with a particular medicament; lower cost thannatural rubber; and reduced leeching of materials from the needle sheathinto the medicament.

[0004] Thermoplastic elastomers also permit a wider choice ofsterilization methods between gases like ethylene oxide, irradiation, orautoclaving. One problem with some synthetic thermoplastic elastomers isthat the particular composition which is most compatible with aparticular medicament has a low permeability to a sterilizing gas.

[0005] Thus, it is desirable to provide a needle sheath that can besterilized using any sterilizing gas while permitting the needle sheathto be composed of any thermoplastic elastomer, including one having alow permeability to the particular sterilizing gas. In addition, it issometimes desirable to produce a needle sheath formed of plastic.Plastics generally have low gas permeability. Thus, it is desirable toprovide a needle sheath that can be formed of materials with low gaspermeability and still be sterilized by a sterilizing gas.

SUMMARY OF THE INVENTION

[0006] In general terms, this invention provides a syringe assemblyhaving a needle sheath that can be formed of a material having a low gaspermeability, but which can be sterilized using a sterilizing gas.

[0007] A syringe assembly designed according to this invention includesa syringe body, a needle cannula, and a needle sheath. The needle sheathhas a body portion with a cavity that is open at a first end and closedat a second end opposite the first end. The cavity receives the needlecannula and includes a passage in communication with-the first end ofthe cavity. The passage has a shape that permits gas from the externalatmosphere to flow into the cavity while simultaneously preventing entryof microorganisms from the external atmosphere into the cavity.

[0008] These and other features and advantages of this invention willbecome more apparent to those skilled in the art from the followingdetailed description of the presently preferred embodiment. The drawingsthat accompany the detailed description can be described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a cross-sectional view of a syringe assembly designedaccording to the present invention;

[0010]FIG. 2 is a cross-sectional view of another embodiment of asyringe assembly designed according to the present invention;

[0011]FIG. 3 is a cross-sectional side view of a needle sheath designedaccording to the present invention;

[0012]FIG. 4 is a cross-sectional view along line 4-4 of FIG. 3;

[0013]FIG. 5 is a cross-sectional side view of another embodiment of aneedle sheath designed according to the present invention;

[0014]FIG. 6 is a cross-sectional view along line 6-6 of FIG. 5;

[0015]FIG. 7 is a cross-sectional side view of another embodiment of aneedle sheath designed according to the present invention;

[0016]FIG. 8 is a cross-sectional view along line 8-8 of FIG. 7;

[0017]FIG. 9 is a cross-sectional side view of another embodiment of aneedle sheath designed according to the present invention;

[0018]FIG. 10 is a cross-sectional view along line 10-10 of FIG. 9;

[0019]FIG. 11 is a cross-sectional side view of another example of aneedle sheath designed according to the present invention; and

[0020]FIG. 12 is a cross-sectional view along line 12-12 of FIG. 11.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0021] A syringe assembly is generally indicated at 20 in FIG. 1. Thesyringe assembly 20 includes a syringe body 22 and a needle sheath 24.The syringe body 22 has an interior chamber 26 that receives amedicament 32 and is in communication with a passage in a neck portion28. An integral needle cannula 30 is supported on the neck portion 28and in communication with the interior chamber 26 through the passage inthe neck portion 28. A conventional stopper 34 and plunger rod 36 areused to eject the medicament 32 from the needle cannula 30 whileadministering an injection in a conventional manner.

[0022] The needle sheath 24 includes a body portion 38 with a cavity 40.The needle sheath 24 has a first end 42 and a second end 44. The firstend 42 defines the cavity opening and is received over the neck portion28. In FIG. 1, the syringe assembly 20 is shown as prefilled syringecontaining the medicament 32 loaded in the interior chamber 26. Ofcourse, the syringe assembly 20 could be packaged without any medicament32 in the interior chamber 26.

[0023]FIG. 2 illustrates another syringe assembly 20 designed accordingto the present invention. The syringe assembly in FIG. 2 does notinclude an integral needle cannula 30, but includes a needle cannula 46extending from a hub 48. The hub 48 and needle cannula 46 are supportedon the neck portion 28 of the syringe body 22.

[0024] A cross-sectional side view of a needle sheath 24 designedaccording to one embodiment of the present invention is shown in FIGS. 3and 4. The cavity 40 has an inner surface 52. Ridges 54 are located onthe inner surface 52 of the cavity 40. Each ridge 54 includes a gap 56.Preferably, the gap 56 has a cross-sectional size that is between about0.00001 and 0.00008 square inches. The gap 56 of adjacent ridges 54 arecircumferentially offset from each other. The amount of offset betweengaps 56 may be varied as needed in a particular situation. In oneexample, only a single ridge 54 is used.

[0025] When the needle sheath 24 is fit over the neck portion 28, theridges 54 sealingly engage the outer surface of the neck portion 28, forexample. The gap 56 provides a passage between the first end 42 and thecavity 40. The size of the gap 56 permits sterilizing gas from outsideof the cavity 40 to flow into the cavity 40 while simultaneouslypreventing undesirable microorganisms from entering the cavity 40.

[0026] The design of this invention permits a syringe assembly 20 to beassembled under non-sterile conditions and to subsequently be sterilizedby a sterilizing gas such as ethylene oxide while using thermoplasticelastomers to form the needle sheath 24. The gaps 56 permit thesterilizing gas to flow into the cavity 40 and to sterilize the interiorof the cavity 40 and either the integral needle cannula 30 or the needlecannula 46.

[0027]FIGS. 5 and 6 illustrate an alternative embodiment of a needlesheath 24 designed according to the present invention. The needle sheath24 includes a groove 58 formed on the inner surface 52 of the cavity 40.The groove 58 has a shape that provides a non-linear pathway from thefirst end 42 into the cavity 40. The nonlinear pathway provided by thegroove 58 permits a sterilizing gas to enter the cavity 40 whilesimultaneously preventing undesirable microorganisms from entering thecavity 40. The groove 58 must extend into the cavity 40 sufficient toallow the sterilizing gas to contact the needle.

[0028] As shown in FIGS. 7 and 8, a groove 58′ could provide a pathwaythat spirals around the inner surface 52 of the cavity 40. In theembodiments shown in FIGS. 5-8 the inner surface 52 of the needle sheath24 will be in sealing engagement with either the neck portion 28 or thehub 48 when the syringe assembly 20 is complete. The groove 58 and 58′,however, allows for the sterilizing gas to enter the cavity 40 during asterilizing process.

[0029] An alternative embodiment of the needle sheath 24 is shown inFIGS. 9 through 12. In FIG. 9, a plurality of ridges 60 are formed onthe inner surface 52 of the cavity 40. A gap 62 is located between theplurality of ridges 60. The gap 62 provides a passage from the first end42 into the cavity 40. The gap 62 permits sterilizing gases to enter thecavity 40 while preventing undesirable microorganisms in the externalatmosphere from entering the cavity 40. In the embodiment shown in FIGS.9 and 10, the ridges 60 and the majority of the inner surface 52 will bein sealing engagement with either the neck portion 28 or the hub 48 whenthe syringe assembly 20 is fully assembled. As shown in FIGS. 11 and 12,the ridges 60 have a shape that provides a spiralling gap 62 around theinner surface 52 of the cavity 40.

[0030] The shape of the passage permitting sterilizing gas to enter thecavity 40 may take a variety of forms. It is imperative that the passagehave some contour or non-linearity so that microorganisms cannot findtheir way into the cavity 40. Otherwise, sterility would not bepreserved. The example passages disclosed in this description providethe necessary two-fold function of allowing gas flow whilesimultaneously preventing microorganism entry.

[0031] The needle sheath 24 can be formed from rubber, thermoplasticelastomers, or plastics. The particular material used to form the needlesheath 24 is selected based on compatibility with the medicament 32 thatis eventually loaded into the syringe assembly 20 and other designconsiderations.

[0032] The foregoing description is exemplary rather than limiting innature. Variations and modifications to the disclosed embodiment maybecome apparent to those skilled in the art and do come within the scopeof this invention. Accordingly, the scope of legal protection affordedthis invention can only be determined by studying the following claims.

We claim:
 1. A needle sheath for a syringe comprising: a body portionhaving a cavity with an opening at a first end and being closed at asecond end opposite said first end; and a passage in communication withsaid first end of said cavity, said passage having a shape that permitsgas from the external atmosphere to flow into said cavity andsimultaneously prevents entry of microorganisms from the externalatmosphere into said cavity.
 2. A needle sheath for a syringe as recitedin claim 1 , wherein said cavity includes an inner surface having atleast one ridge extending into said cavity from said inner surface andsaid passage comprises a gap in said ridge.
 3. A needle sheath for asyringe as recited in claim 2 , further comprising a plurality of saidridges, each said ridge extending around the entire circumference of theinner surface, each said ridge including a gap and wherein said gaps arecircumferentially offset from each other.
 4. A needle sheath for asyringe as recited in claim 2 , wherein said gap has a cross-sectionalsize that is between about 0.00001 and 0.00008 square inches.
 5. Aneedle sheath for a syringe as recited in claim 1 , wherein said cavityincludes an inner surface and said passage comprises a non-linear grooveformed in said inner surface.
 6. A needle sheath for a syringe asrecited in claim 5 , wherein said passage shape includes a spiral aroundsaid inner surface.
 7. A needle sheath for a syringe as recited in claim1 , wherein said passage comprises a gap between a plurality of ridges,said ridges formed on an inner surface of said cavity.
 8. A needlesheath for a syringe as recited in claim 1 , wherein said needle sheathcomprises rubber.
 9. A needle sheath for a syringe as recited in claim 1, wherein said needle sheath comprises a thermoplastic elastomer.
 10. Aneedle sheath for a syringe as recited in a claim 1 , wherein saidneedle sheath comprises a plastic.
 11. A syringe assembly comprising: asyringe body; a needle cannula supported by said syringe body; a needlesheath having a body portion, said body portion having a cavity with anopening at a first end and being closed at a second end opposite saidfirst end, said cavity receiving said needle cannula, said cavity beingsupported on and sealingly engaging said syringe body; and a passage incommunication with said first end of said cavity, said passage having ashape that permits gas from the external atmosphere to flow into saidcavity and simultaneously prevents entry of microorganisms from theexternal atmosphere into said cavity.
 12. A syringe assembly as recitedin claim 11 , wherein said needle cannula is formed integral with saidsyringe body.
 13. A syringe assembly as recited in claim 11 , whereinsaid cavity includes an inner surface having at least one ridge and saidpassage comprises a gap in said ridge.
 14. A syringe assembly as recitedin claim 13 , wherein said ridge is annular.
 15. A syringe assembly asrecited in claim 14 , wherein said gap has a cross-sectional size thatis between about 0.00001 and 0.00008 square inches.
 16. A syringeassembly as recited in claim 14 , further comprising a plurality of saidridges each having said gap and wherein said gaps are circumferentiallyoffset from each other.
 17. A syringe assembly as recited in claim 11 ,wherein said cavity includes an inner surface and said passage comprisesa non-linear groove formed in said inner surface.
 18. A syringe assemblyas recited in claim 17 , wherein said passage shape includes a spiralaround said inner surface.
 19. A syringe assembly as recited in Claim 11, wherein said passage comprises a gap between a plurality of ridges,said ridges formed on an inner surface of said cavity.
 20. A syringeassembly as recited in claim 19 , wherein said passage shape includes aspiral around said inner surface.